ABSTRACT:

Calla palustris L., despite its wide distribution in the Northern Hemisphere, is poorly understood with respect to its ecology. We made observations on the flowering sequence and on floral visitors in a natural population in the Vosges, France, and conducted mating system experiments in the Botanical Garden of the University of Vienna. The anthesis of Calla inflorescences lasted approximately ten days. It started by a female phase with stigmas becoming receptive from the base to the top of the inflorescences. Stamen dehiscence followed the same pattern and the male phase started towards the end or after completion of the female phase. Our experiments showed that Calla is at least partly self-pollinated or apomictic, as ca. 20 % of the gynoecia developed into fruits and produced seeds without pollinators. Entomophily cannot be excluded, as we observed few small Coleoptera and Diptera visiting the inflorescences. Anemophily, although less probable, remains to be tested.